Two baby gorillas have been born at the Wildlife Conservation Society’s Bronx Zoo in New York City. They are the first baby western lowland gorillas born at the zoo since 2006.

The babies, whose genders are not yet known, were born to two mothers: 33-year-old Julia and 19-year-old Tuti. Ernie, a 31-year-old western lowland gorilla, is the father to both.

“The gestation period for a gorilla is 8.5 months and newborns weigh approximately 4 to 5 pounds,” the Bronx Zoo said in a release. “Gorilla infants are held by their mother for the first four months of their life. Infants start eating solid foods at about 6 months but will nurse until they are 3 or 4 years old.

Visitors will be able to see the babies later this spring, dependent upon weather, temperature, and other factors, the zoo says.

Western lowland gorillas are designated as Critically Endangered by the International Union for Conservation of Nature.